At present, consumer demands are focused more on safety, reliability, convenience, efficiency and state of the art of technology and not solely on the cost. Consequently, many new technologies are being implemented to meet such attributes of various applications. Green products or electronics can be considered as an ideal example, and they are intended to curtail the adverse effects of carbon footprint, over use of fossil fuels and associated environmental pollution, etc.
Within a very short time period, many green energy regulations have been introduced and billions of dollars have been invested worldwide in green energy related research and development projects in search for efficient, cost-effective, and reliable green technologies. Amongst these green energy technologies, distributed energy generation (DG) using renewable energy sources, is regarded as one of the best solutions for meeting energy requirements while minimizing the carbon footprint. However, the optimal and efficient use of DG systems, especially in units based on wind and solar power, are largely affected by the stochastic nature of their energy production. Consequently, large and expensive storage systems are required to alleviate such fluctuations and meet the demand in the most efficient way. As a cost-effective alternative storage system, the vehicle to grid (V2G) concept, which uses electric vehicles (EV) to store and supply energy to the grid, is gaining more and more popularity as the vehicle has now become an indispensable component in both “living and mobility”.
Traditionally, EVs are charged through a wired connection between the utility grid and the vehicle. However, recent advancements in contactless inductive power transfer (IPT) techniques have made contactless charging of EVs an economically viable solution. Although contactless charging of EVs is still expensive in comparison to wired charging, it offers advantages in relation to reliability, safety and convenience. Thus, contactless charging of electric vehicles is becoming popular as an effective and efficient means of charging EVs.
Existing single-phase bi-directional and uni-directional IPT systems (such as those disclosed in WO 2010/062198) can be used to charge and/or discharge multiple EVs using one IPT primary power source. However, such prior art systems are incapable of energising individual primary (charging) pads/windings/coils/couplers, which are connected in series and powered by one primary supply, and magnetically coupled to pick-up pads (windings/coils) of multiple EVs, to allow for selective charging and/or discharging EVs as required. The selective charging of EVs can be achieved by using a dedicated IPT system, comprising a primary power supply and a primary charging pad which is magnetically coupled to a pick-up pad, for each EV but this is expensive as multiple systems are required for charging multiple EVs. In contrast, the capability of selective charging/discharging of multiple EVs using a single IPT primary power supply is cost effective, and improves efficiency, reliability and safety as each primary pad is energised only when a corresponding EV is to be charged or discharged. Applications that benefit from this capability include charging bays located in public areas, for EVs and dynamic charging/discharging of moving EVs.
Alternatively, efficiency in wireless charging of EVs and similar loads may be improved by employing a poly-phase IPT system. However, existing three-phase IPT systems generally utilise a three-phase primary system but only a single-phase pick-up system with a single pad, and/or suffer from one or more of the disadvantages of limited (if any) or sub-optimal control, flexibility, versatility and overall efficiency.